bp2build remove "-std" from cflags

Soong overrides "-std" flags when provided via cppflags or conlyflags;
however, any user-provided "-std=" cflag will be overridden by Soong's
std flag handling.

For Bazel, we _always_ allow user to override via user provided flags.
To prevent conflicts, we remove the silently ignored values from
Android.bp files in the bp2build conversion.

Test: build/bazel/ci/bp2build.sh
Test: build/bazel/ci/mixed_droid.sh
Change-Id: I4c33b2ae593a7ff3ff8e3ad15ef3461354fc0c83

android/bazel.go

@@ -364,8 +364,6 @@ var (
 
 	// Per-module denylist to always opt modules out of both bp2build and mixed builds.
 	bp2buildModuleDoNotConvertList = []string{
-		"libnativehelper_compat_libc++", // Broken compile: implicit declaration of function 'strerror_r' is invalid in C99
-
 		"libandroid_runtime_lazy", // depends on unconverted modules: libbinder_headers
 		"libcmd",                  // depends on unconverted modules: libbinder
 

bp2build/cc_library_static_conversion_test.go

@@ -1433,3 +1433,21 @@ func TestCcLibraryStaticUseVersionLib(t *testing.T) {
 		},
 	})
 }
+
+func TestCcLibraryStaticStdInFlags(t *testing.T) {
+	runCcLibraryStaticTestCase(t, bp2buildTestCase{
+		blueprint: soongCcProtoPreamble + `cc_library_static {
+	name: "foo",
+	cflags: ["-std=candcpp"],
+	conlyflags: ["-std=conly"],
+	cppflags: ["-std=cpp"],
+	include_build_directory: false,
+}`,
+		expectedBazelTargets: []string{
+			makeBazelTarget("cc_library_static", "foo", attrNameToString{
+				"conlyflags": `["-std=conly"]`,
+				"cppflags":   `["-std=cpp"]`,
+			}),
+		},
+	})
+}

cc/bp2build.go

@@ -162,7 +162,7 @@ func bp2buildParseStaticOrSharedProps(ctx android.BazelConversionPathContext, mo
 	attrs := staticOrSharedAttributes{}
 
 	setAttrs := func(axis bazel.ConfigurationAxis, config string, props StaticOrSharedProperties) {
-		attrs.Copts.SetSelectValue(axis, config, props.Cflags)
+		attrs.Copts.SetSelectValue(axis, config, parseCommandLineFlags(props.Cflags, filterOutStdFlag))
 		attrs.Srcs.SetSelectValue(axis, config, android.BazelLabelForModuleSrc(ctx, props.Srcs))
 		attrs.System_dynamic_deps.SetSelectValue(axis, config, bazelLabelForSharedDeps(ctx, props.System_shared_libs))
 
@@ -279,9 +279,18 @@ type compilerAttributes struct {
 	protoSrcs bazel.LabelListAttribute
 }
 
-func parseCommandLineFlags(soongFlags []string) []string {
+type filterOutFn func(string) bool
+
+func filterOutStdFlag(flag string) bool {
+	return strings.HasPrefix(flag, "-std=")
+}
+
+func parseCommandLineFlags(soongFlags []string, filterOut filterOutFn) []string {
 	var result []string
 	for _, flag := range soongFlags {
+		if filterOut != nil && filterOut(flag) {
+			continue
+		}
 		// Soong's cflags can contain spaces, like `-include header.h`. For
 		// Bazel's copts, split them up to be compatible with the
 		// no_copts_tokenization feature.
@@ -308,10 +317,14 @@ func (ca *compilerAttributes) bp2buildForAxisAndConfig(ctx android.BazelConversi
 	ca.absoluteIncludes.SetSelectValue(axis, config, props.Include_dirs)
 	ca.localIncludes.SetSelectValue(axis, config, localIncludeDirs)
 
-	ca.copts.SetSelectValue(axis, config, parseCommandLineFlags(props.Cflags))
-	ca.asFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Asflags))
-	ca.conlyFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Conlyflags))
-	ca.cppFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Cppflags))
+	// In Soong, cflags occur on the command line before -std=<val> flag, resulting in the value being
+	// overridden. In Bazel we always allow overriding, via flags; however, this can cause
+	// incompatibilities, so we remove "-std=" flags from Cflag properties while leaving it in other
+	// cases.
+	ca.copts.SetSelectValue(axis, config, parseCommandLineFlags(props.Cflags, filterOutStdFlag))
+	ca.asFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Asflags, nil))
+	ca.conlyFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Conlyflags, nil))
+	ca.cppFlags.SetSelectValue(axis, config, parseCommandLineFlags(props.Cppflags, nil))
 	ca.rtti.SetSelectValue(axis, config, props.Rtti)
 }